UNUSUAL X-RAY ABSORPTION-SPECTROSCOPY AT THE CERIUM LIII EDGE IN CERIUM NITRIDE

Photoemission and photoabsorption experiments have been carried out on the 2p level in cerium nitride. Whereas strong final-state satellites are observed on the 2p-XPS spectrum indicating an important mixture of 4f1 and 4f0 configurations in the ground state, the L(III) edge spectrum only exhibits a white line that is usually interpreted as the signature of a trivalent configuration. This apparent contradiction between the two spectroscopies indicates that the phenomenological approach of Ce-L(III) edge is inappropriate for CeN. We discuss these absorption experiments in the framework of a Gunnarsson-Schonhammer model modified to include the interaction between the photoelectron and the system. We show that the unusual L(III) edge observed in cerium nitride results from the peculiar band structure encountered in this compound.